1. Field of the Invention
The present invention relates generally to therapeutic placement of endoluminal coils, and more particularly to a coil delivery system having a mechanical latch.
Endoluminal coils have a wide variety of existing and proposed therapeutic uses. Existing therapies often make use of endovascular coils, for example, in the treatment of vascular aneurysms. Aneurysms are the result of abnormal dilation of a blood vessel, usually resulting from disease and/or genetic predisposition, which can weaken the arterial wall and allow it to expand. In vasooclusion coil therapy, a number of coils are typically placed within the aneurysm to occlude the site by posing a physical barrier to blood flow, and by promoting the formation of thrombus.
The use of coils has recently been proposed to provide contraception or permanent sterilization. Contraceptive intrafallopian coils can be anchored within the isthmus of the fallopian tube to occlude the tube and prevent conception. Anchoring of intrafallopian coils is enhanced by providing a helical outer surface, while the efficacy of an intrafallopian coil as a contraceptive is improved by including copper with the coil. Exemplary contraceptive intrafallopian coils are described in copending U.S. patent application Ser. Nos. 08/474,779 and 08/475,252 (Attorney Docket Nos. 16355-24 and 16355-25), the full disclosures of which are hereby incorporated by reference.
Coils have typically been placed at the desired site within body lumens using a catheter and a pusher. The catheter is first positioned near the site, typically using a guidewire under fluoroscopy, ultrasound, or the like. Once the site has been reached, the guidewire is removed. The coil is then inserted into the proximal end of the catheter lumen and advanced through the catheter using a pusher. Pushers are typically simple wires having a distal end that is adapted to advance the coil. When the coil reaches the distal end of the catheter, it is discharged from the catheter by advancing the pusher, or alternatively by axially restraining the pusher and retracting the catheter from around the coil. When using a standard catheter and pusher delivery system, coils are simultaneously decoupled from the delivery catheter and released from a straight configuration.
Endoluminal coils are generally resilient structures which are biased to form bent secondary shapes when released. The coils are restrained by the catheter wall in a relatively straight configuration, allowing the resilient coils to be advanced along narrow, torturous luminal paths. As the coil advances out the distal end of the catheter, it tries to assume its relaxed, bent shape, which is typically larger in cross-section than the body lumen in which the coil is being positioned. The resilient force of the released coil against the lumen wall anchors the coil within the lumen.
Although the release of endoluminal coils using catheters and pushers has proven effective, the technique suffers from a number of undesirable limitations. First, the position of the coil at the site cannot be controlled to a fine degree of accuracy. While the coil is restrained in a straight configuration, it extends along a considerable length of the body lumen. As the coil is released, it will anchor against the lumen wall somewhere along this length. However, the coil in its relaxed state will extend along a much shorter length of lumen, and the final location of the released, convoluted coil along the body lumen is difficult to predict. Second, once the coil has left the catheter, it is difficult to reposition or retrieve the coil. Third, the use of a catheter and pusher release technique for anchoring of helically surfaced coils within body lumens is problematic. The catheter wall prevents the helical shape from seating while the coil is in the straightened configuration, and the pusher/coil interface does not allow torquing of the coil to seat the helical shape against the lumen wall.
For these reasons, it is desirable to provide effective, reliable endoluminal delivery systems and methods for their use. It would be particularly desirable if such delivery systems promoted the precise positioning of a coil within a body lumen, preferably by providing separate coil coupling and release mechanisms. Ideally, such systems and methods would allow a retrieval of a partially anchored coil from within the body lumen. It would be further desirable if coil delivery systems were provided which allowed torquing of a helically shaped intrafallopian coil to anchor the coil against the fallopian tube.
2. Description of the Related Art
U.S. Pat. No. 5,250,071 describes an embolic coil delivery device using a series of interlocking clasps pinned together with a control wire. U.S. Pat. Nos. 5,261,916 and 5,304,195 describe detachable pusher-vasoocclusive coil assemblies having interlocking ball couplings. Release of each of these coils is accomplished by advancing the coupling beyond the end of a restraining catheter.
U.S. Pat. No. 5,234,437 describes a detachable pusher vasoocclusion coil assembly having a threaded coupling which provides release of the coil on rotation of the pusher U.S. Pat. No. 5,312,415 describes a similar pusher/coil coupling.
U.S. Pat. Nos. 5,122,136 and 5,354,295 describe electrolytically detachable guidewire tips for the endovascular formation of thrombus. U.S. Pat. No. 5,108,407 describes an embolic coil pusher apparatus having a heat releasable adhesive bond which is decoupled using laser energy transmitted along a fiber optic cable. U.S. Pat. Nos. 3,868,956 and 4,994,069 are also generally relevant.
The experimental use of a stainless steel intrafallopian device is described in "Transcatheter Tubal Sterilization in Rabbits," penny L. Ross, RT 29 Investigative Radiology, pp. 570-573 (1994). The experimental use of an electrolytically pure copper wire as a surgical contraceptive intrafallopian device in rats was described in "Antifertility Effect of an Intrafallopian Tubal Copper Device," D. N. Gupta, 14 Indian Journal of Experimental Biology, pp. 316-319 (may 1976).
U.K. Patent Application pub. No. 2,211,095 describes a uterine screw plug for blocking the fallopian tube. European Patent Application pub. No. 0,010,812 describes a device for placement in the oviducts having enlargements at either end for anchoring the device. The same device appears to be described in Netherlands Patent No. 7,810,696.